NOVEL TUNABLE BRANCH-LINE COUPLER FOR WLAN APPLICATIONS

In this article, a tunable branch-line coupler with a novel structure is designed to operate at 5.7GHz. A design method is based on miniaturization method with adjusting the resonance frequency. The proposed coupler without taped line feed structures operated at 5.62 GHz, and it has a size of 55.8 mm 2 while its performance is reasonable. To improve the performance, the taped line feed structures are added. The wideband response exhibits that the proposed coupler acts properly with the spurious harmonics up to 11.4 GHz. In addition, at 5.7 GHz, the good insertion loss (2.3 dB) and coupling factor (2.6 dB) are obtained. The proposed coupler is simulated, fabricated, and measured. The results show that there is a good agreement between the simulation and measurement results. (C) 2015 Wiley Periodicals, Inc.